Regulatory T cells (Tregs) are immune cells that function to regulate the immune system in order to prevent autoimmune disease. They do this by sustaining immune tolerance to the body’s own cells and antigens. Tregs are known to have interleukin 2 receptors (IL-2R), and their functions depend on interleukin 2 (IL-2), a cytokine that is released by T helper cells and act on cytotoxic T cells.